Bake pie crust at 400°F for 10 minutes. Set aside.
In medium mixing bowl, blend coconut milk, lemon juice, lemon monk fruit, 3 egg yolks, and glucomannon with electric mixer.
Spread filling into baked pie crust. Shield edges with foil or a pie shield and bake at 350°F for about 10 minutes or until custard is soft set.
In a clean mixing bowl with clean beater, whip the 3 egg whites with the vanilla extract and cream of tartar at medium speed until soft peaks form. Gradually add the low carb granular sweetener a little at a time on high speed until stiff glossy peaks form.
Spread over lemon filling and make several peaks with the back of a spoon.
Bake at 350°F for 10 minutes. Cool on rack before refrigerating.
Use a clean mixing bowl to beat egg whites. Even a little oil or yolk in thee bowl can prevent the whites from beating to stiff peaks.Cover the pie crust edges with a pie shield or aluminum foil. Keto pie crusts tend to burn easily so it's best to keep the edges covered.